add TTL for label cache

[dreamerlzl]

see #3019

[brancz]

If I recall correctly I think we had this cache in the old agent because we wanted to re-resolve metadata every now and then, eg. if an annotation was added to a pod at runtime. I feel like a 15s TTL might be a little too aggressive for this though. I think maybe a 10min TTL is more appropriate as this should really only be necessary quite rarely.

[dreamerlzl]

If I recall correctly I think we had this cache in the old agent because we wanted to re-resolve metadata every now and then, eg. if an annotation was added to a pod at runtime. I feel like a 15s TTL might be a little too aggressive for this though. I think maybe a 10min TTL is more appropriate as this should really only be necessary quite rarely.

Yeah we have the similar use cases. I have changed the default value to 10min